1. Technical Field
The present invention relates to a semiconductor device and a method for fabricating the same. More particularly, the present invention relates to a semiconductor device having an isolation layer formed by a shallow trench isolation (STI) method, and a method for fabricating the semiconductor device.
2. Related Art
FIGS. 1A to 1C illustrate a conventional fabrication process of a semiconductor device.
Referring to FIG. 1A, a pad oxide layer 13, a pad nitride layer 15, and a capping layer 17 are sequentially formed on a semiconductor substrate 11. Capping layer 17, pad nitride layer 15, and pad oxide layer 13 are patterned by a photolithography method, thus exposing portions of semiconductor substrate 11.
Referring to FIG. 1B, the exposed portions of semiconductor substrate 11 are dry-etched by using capping layer 17 as an etch mask, thereby forming trenches 19.
Referring to FIG. 1C, insulating material, such as silicon oxide, may be deposited over capping layer 17, so that trenches 19 are gap-filled. Then, the insulating material is polished to expose capping layer 17, thereby forming isolation layers 21 remaining within trenches 19. Capping layer 17, pad nitride layer 15, and pad oxide layer 13 are then removed by wet etch.
However, in the semiconductor device fabricated according to the conventional art, the thickness of a gate insulating layer to be formed later may not be uniform, and may be thin at the edges of isolation layers 21. Thus, a strong electric field may be realized at the edges of isolation layers 21 when the semiconductor device operates. Accordingly, the lifespan of the semiconductor device may be shortened, because the gate insulating layer may easily be degraded and/or broken.